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Pump inlet restriction

Pump inlet restriction

Pump inlet restriction

(OP)
I'm adding a feature to a machine for doing fluid exchanges. The current pump is a 12vdc diaphragm pump self priming up to 12 ft vertical. The problem that on the suction side there needs to be a diverter valve then filter then 10 feet of tube (3/8" ID currently, size not fixed) a 'Y' assembly and 5 feet of 5/16" od tube (size fixed). It then just dumps fluid into a waste tank. All this restriction on the inlet is slowing the machine down drastically.  Any suggestions for better pump selection etc to improve performance?   

RE: Pump inlet restriction

Get a slower pump or increase the diameter of the suction lines.  You can only get so much waste thorugh a tube when operating with low pressure drop constraints.  A diaphram pump is also susceptible to acceleration head requirements in the suction line and a larger diameter is very beneficial, as is lowering the speed.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Pump inlet restriction

Improve the suction line with one or more of the following inputs (they will all be beneficial contributing to increasing the NPSHa):
    Increase the static head (height of the suction tank)
    Locate the pump close to the suction tank.
    Increase the diameter of the suction line
    
The presence of a dampener in the suction line to mitigate pulsation could lead to some benefits from the point of view acceleration losses.
A pump configuration which foresees two heads oriented 180° out phase will also help to mitigate pulsation effect.
 

RE: Pump inlet restriction

(OP)
Would a gear pump be a good choice for this application.  To the other response the inlet tube diamter is fixed, it is the largest diameter that will still fit into the recepticle.

RE: Pump inlet restriction

Possibly a gear pump may work better.  It tends to run with a more constant liquid velocity than a pd pump, but since I think the real problem is suction line diameter and low available pressures, you may not see any noticable improvement. If you can't raise the suction tank level, as ione suggested, I'm afraid you have a difficult situation.


Out of box solutions?

Can you use a submersible pump located in the waste source tank?

Can you add a small quantity of something (water? or other fluid) to the waste to decrease its specific gravity and viscosity while still having a total flowrate within the pump's flowrate range.


 

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Pump inlet restriction

12 vdc with 3/8" tubing? This sounds like a lab bench setup. ione's comments are apropos. You might also want to take a look at peristaltic pumps. If you get the right models, they have the ability to dial in variable speeds and hence heads and flows.  

RE: Pump inlet restriction

(OP)
On the suction side all I can do is get a diverter valve that is less restrictive and same with the filter.  The inlet lines sizes are fixed, and there is no access to do anything in the waste tank besides inserting the 5/16" od tube.  So I'm really just looking for the best style of pump to be using, also it's a very cost sensitive application.

RE: Pump inlet restriction

gscully,

Why the filter? Diaphragm pumps's speciality is to pump fluids with high solids concentration. The only reason for a filter is that the particles size is too big to pass the valves. What valves are installed, flapper or ball checks? If the particle size can be too big and if that is the reason for the filter, is the filter monitored? If not, it will clog and that creates more friction on the suction side than anything else. A bigger and/or shorter pipe will not solve the problem and a suction side pulsation dampener neither. So, tell us a little bit more about the particles that are in your fluid and about the valves inside the pump.  

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